Glyphosate and Bt Proteins Toxic to Stingless Bees

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Glyphosate and Bt Proteins Toxic to Stingless Bees

Brazil is the second largest producer of genetically modified (GM) plants in the world. This agricultural practice exposes native pollinators to contact and ingestion of Bacillus thuringiensis proteins (e.g. Cry toxins) from transgenic plants. Furthermore, native bees are also exposed to various herbicides applied to crops, including glyphosate.

Various bee species are suffering large population declines. Stingless bees are important wild pollinators which have a life history which makes them more susceptible to the effects of agrochemicals, compared to other bees.

A study found that the Bt proteins Cry1F and Cry2Aa, and glyphosate were highly toxic to the stingless bee M. quadrifasciata, causing lethal or sublethal effects which can severely impair colony growth and viability, and reduce pollination ability. Glyphosate was very toxic to the bee larvae, killing all of them within only a few days of exposure while bees treated with Cry2Aa and Cry1F proteins were delayed in their development.

This study underscores the need for further research to establish trustworthy methods of assessing the risks of glyphosate and Cry proteins for non-target species.

Brazil is the second largest producer of genetically modified plants in the world. This agricultural practice exposes native pollinators to contact and ingestion of Bacillus thuringiensis proteins (e.g. Cry toxins) from transgenic plants. Furthermore, native bees are also exposed to various herbicides applied to crops, including glyphosate. Little is known about the possible effects of glyphosate and Cry proteins on stingless bees, especially regarding exposure at an immature stage. Here, we show for the first time that glyphosate is lethal, and that Cry toxins (Cry1F, Cry2Aa) alter the development of the stingless bee Melipona quadrifasciata upon contamination of larval food. Glyphosate was very toxic to the bee larvae, killing all of them within only a few days of exposure. Bees treated with Cry2Aa proteins had a higher survival rate and were delayed in their development, compared to the negative controls. Those treated with the Cry1F protein also suffered delays in their development, compared to the negative controls. In conclusion, the proteins Cry1F, Cry2Aa, and the herbicide glyphosate were highly toxic to the stingless bee M. quadrifasciata, causing lethal or sublethal effects which can severely impair colony growth and viability, and reduce pollination ability.

Conclusions

This study provides information about the potential risks of GM crops on a wild pollinator. The methods were suitableforrisk assessment and can also be adapted to conduct further research on other toxins produced by GM crops. Glyphosate and GM crops are widely used in Brazil, which is a country of considerably high biodiversity, and has vast areas of pollinator-agricultural interface.

The lack of tests on the effects of glyphosate and Bt toxins on bee larvae and mature stingless bees complicate the introduction of conservation strategies for this important group of pollinators. As pointed out previously, stingless bees have a life history which makes them more susceptible to the effects of agrochemicals, compared to other bees (Lima et al., 2016), therefore risk assessments regarding GM crops should include various toxicological tests, and must be performed on various species. Thus, our work lays a foundation for further research which should be developed in this particular ﬁeld to establish trustworthy methods of assessing the risks of glyphosate and Cry proteins for non-target species.